1. Field of the Invention
The present invention relates to a damping device for converting dynamic energy into thermal energy of fluid concomitant with a relative shift between two points of building structure etc., for example, and damping it.
2. Description of the Related Art
As a conventional device for damping a dynamic energy for relatively shifting between two members (two points) of building structure etc. concomitant with a swing or a vibration due to an earthquake, a traffic vibration or wind, there is provided a device using a method in which this relative motion is converted into rotary motion of a rotary member, and further, due to heat generation by a frictional resistance of viscous fluid contacting with the rotary member, the dynamic energy concomitant with the above-described shift is converted into the thermal energy of viscous fluid, which is the result of the heat generation, and is damped.
Such a damping device is disclosed in, for example, Japanese Patent Application Laid-open No. Hei 10-184757 and Japanese Patent Application Laid-open No. Hei 10-184786.
The damping device shown in these publication is provided with a casing coupled with one of two points, viscous fluid contained within this casing, a rotary member received rotatably within this casing, a screw nut mechanism (double speed mechanism) interposed between the rotary body and the other of the two points.
This screw nut mechanism is composed of a screw shaft coupled to the other of the two points and a nut connected to the above-described rotary member and threadedly engaged with the screw shaft.
In the thus constructed damping device, the screw shaft is shifted in the axial direction relative to the casing upon the generation of the dynamic energy concomitant with the relative shift between the object portions. Then, the rotary member is rotated by the screw engagement action between the screw shaft and the nut and the viscous fluid contacting this rotary member is heated by means of frictional resistance or the like. As a result, the above-described dynamic energy is converted into the thermal energy of the viscous fluid and is damped.
In the above-described damping device, in order to keep the damping performance in a good condition to prevent the above-described viscous fluid from leaking to the outside, a sealing unit (seal member) is interposed between the above-described casing and the rotary member.
The viscous fluid is heated and expanded by the thermal energy that is converted from the dynamic energy and the pressure is increased to thereby impose an excessive load onto the sealing unit, resulting in a reduction shortage in service life of the sealing unit or the generation of leakage exceeding a suitable level.
In particular, in case of structures in which the rotary member is rotated at a high speed by the screw nut mechanism or the like to enhance the conversion rate to thermal energy, like the damping device disclosed in the publications, the temperature elevation and the pressure increase are great so that the adverse affect against the sealing unit would be great.
In order to overcome the above-noted defects, an object of the present invention is to suppress an adverse affect concomitant with the pressure increase of the viscous fluid to a sealing unit provided in a damping device and to enhance reliability or durability of the damping device.
In order to attain this and other objects, according to the present invention, there is provided a damping device comprising: a container connected to one of two points that move relatively to each other; a moving member coupled to the other of the two points and received relatively movably within the container; a sealing unit retained movably in a gap between the container and the moving member to form a sealed space within the container; fluid received within the sealed space, to be heated by a frictional resistance from the container and the moving body in correspondence with the relative shift between the moving member and the container, as a result to convert into a thermal energy a dynamic energy in correspondence with the relative shift between the two points; and a biasing means for biasing toward the sealed space the sealing unit for moving in response to the pressure of the fluid received in the sealed space, thereby converting a volume of the sealed space.
Thus, the sealing unit is retained movably within the gap so that the sealing unit receiving the pressure moves in a direction in which the volume of the sealing space is increased against the biasing force by the biasing means when the pressure is increased by the heat of the fluid or the like, to thereby suppress the excessive pressure increase of the fluid, and when the pressure of the fluid is decreased, the sealing unit is moved in a direction in which the volume of the sealed space is decreased to suppress the decrease of the pressure of the fluid.
Also, according to another aspect of the present invention, there is provided a damping device comprising: a container connected one of two points that move relatively to each other; a moving member coupled to the other of the two points and received relatively movably within the container; a sealing unit retained in a gap between the container and the moving member to form a sealed space within the container; fluid received within the sealed space, to be heated by a frictional resistance from the container and the moving body in correspondence with the relative shift between the moving member and the container, as a result to convert into a thermal energy a dynamic energy in correspondence with the relative shift between the two points; and a fluid retainer chamber connected to the sealed space for making it possible to pass the fluid between the fluid retainer chamber and the sealed space.
With such an arrangement, the fluid may flow between the sealed space and the fluid retainer chamber when the volume change occurs in accordance with a temperature change of the fluid to thereby make it possible to suppress the pressure change of the fluid.
The connecting portion of the sealed space and fluid retainer chamber is positioned in the vicinity of the sealing unit whereby even if the transmission property of the pressure of the viscous fluid is low, the pressure of the viscous fluid in the vicinity of the sealing unit may be suppressed and the excessive pressure to the sealing unit may be suppressed.
It is preferable that the fluid retainer chamber may comprise a pressure responsible means for moving within the fluid retainer chamber in response to the pressure and for changing the volume of the fluid receiving portion in the fluid retainer chamber.
For example, a piston or a diaphragm is used as the pressure responsible means. When the fluid pressure is increased, the means changes in position and increases the volume of the fluid receiving portion to suppress the increase of the pressure of the fluid.
It is also preferable that the fluid retainer chamber is formed in the interior of the moving member or the side wall portion to simplify the structure of the damping device to provide a compact structure without any projection to the outside. With the pressure responsible means, it is possible to release the fluid retainer chamber to the atmospheric pressure.
Otherwise, in the case where the fluid retainer chamber is kept under the sealed condition, the gas is filled in the interior and it is possible to pressurize the fluid retained in the interior through the pressure responsible means at a predetermined pressure toward the sealed space.
It is preferable that the fluid retainer chamber comprises a bellows for expanding and shrinking in response to the pressure of the fluid introduced therein and for changing the volume of the fluid receiving portion. This makes it possible to provide a simpler structure with a high operational stability.
Also, according to still another aspect of the present invention, there is provided a damping device comprising: a container connected to one of two points that move relatively to each other; a moving member coupled to the other of the two points and received relatively movably within the container; a sealing unit retained in a gap between the container and the moving member to form a sealed space within the container; fluid received within the sealed space, to be heated by a frictional resistance from the container and the moving body in correspondence with the relative shift between the moving member and the container, as a result to convert into a thermal energy a dynamic energy in correspondence with the relative shift between the two points; and an elastic member exposed in a part of a wall surface defining the sealed space and changing a volume in response to a pressure applied from the fluid.
This elastic member is disposed in the concave portion provided in a part of the wall surface defining the sealed space, for example. When the pressure fluid is increased, the volume is decreased to increase the volume of the sealed space to suppress the increase of the fluid pressure.
The elastic member is disposed in the vicinity of the sealing unit whereby even if the fluid is the viscous fluid and the transmission property of the pressure is low, the pressure of the fluid in the vicinity of the sealing unit is suppressed and the application of the excessive pressure to the sealing unit may be suppressed.
The elastic member is made of rubber elastic material, for example, and it is possible to use any shape such as a solid form, a hollow form or a foamed form.
It is preferable that the fluid comprises viscous fluid; the moving member comprises a rotary member received rotatably within the container; and the rotary member comprises a screw shaft coupled with the other of the two points and a nut connected to the rotary member and threadedly engaged with the screw shaft and the rotary member is coupled with the other of the two points through a rotary mechanism for converting a reciprocating motion of the screw shaft into a rotary motion of the rotary member.
With the rotary mechanism, the relative shift between the two points is converted into the rotary motion, the frictional resistance by the viscous fluid is increased so that the conversion efficiency to the thermal energy may be set at a high level to enhance the damping effect.
According to the present invention, it is possible to suppress the adverse affect concomitant with the pressure increase of the fluid against the sealing unit provided in the damping device to make it possible to enhance reliability and durability of the damping device.